13 Benefits of the Marimo Moss Ball

Live plants are very beneficial for aquariums. They do everything from absorb toxic nitrates to give your animals a natural, beautiful environment to live in. Unfortunately, not all of us have green thumbs. Over the years, I have struggled to keep live plants in my aquariums, even easy ones like Anacharis and Jungle Val, both of which have died on me.

So what’s one to do? Out of all the live plants I have had in my aquariums, there is one plant (well, sort of plant) that has not failed me: the Marimo moss ball.

The moss ball is not to be confused with cheap knockoffs (Java wrapped around plastic or foam spheres). Instead, Marimo moss balls are little squishy balls of algae that look a lot like moss, hence the name. In the wild, they roll along the bottoms of rivers, giving them their round shape. They are also viewed as charms in Japan, and even treated as pets.

Aside from its unique appearance, here are some benefits of having a Marimo moss ball in your aquarium.

Marimo Moss Ball Basic Facts

In addition to regular water maintenance, squeeze the ball very occasionally, and rotate it to make sure all sides are exposed to light
$18 - 23
Very low-maintenance, almost indestructible
Keep in cooler temperatures, away from too much light
Other creatures
The plant is snail-safe, beloved by most other creatures. Goldfish may eat it
With proper care, Marimo can last for over a century
Mostly found in lakes in the northern hemisphere
Growth rate
Very slow, only 5 mm / year

Benefits of the Marimo

1. Sucks Up Nitrates and Other Nasties

Byproducts of fish waste, nitrates are harmless to most healthy fish under 30ppm, but as their numbers increase over time, they can stress and kill your fish. Partial water changes are performed to keep nitrates in check.

Like live plants, moss balls absorb nitrates. But—also like plants—it’s usually not a large amount. The ball would make a difference only if it were kept in just a few gallons of water. Still, any nitrate absorbent is a benefit to your tank’s ecosystem. Moss balls are also like little filters, sucking up debris and small amounts of ammonia and phosphates.

2. Provides Some Oxygen

Like plants in general, moss balls suck up CO2 and release oxygen in the water. If you don’t like noisy air stones, some Marimo moss balls are a great addition to help you oxygenate your tank.

3. Helps Prevent Excess Algae Growth

What better way to combat algae than with algae? Marimo moss balls suck up the same nutrients as undesirable algae, depriving invasive algae of those nutrients. I had brown algae growing in my 10-gallon tank, but since wiping them off the glass and adding a few moss balls, they have yet to grow back. Of course, moss balls won’t make that much of an impact in larger aquariums unless you get more a lot of them. I don’t know about killing off algae, but they can help prevent unwanted algae from growing back.

4. Harbors a Good Amount of Beneficial Bacteria

While gravel and filter media is the most valuable seeding items for a new tank, the Marimo moss ball, like many plants, has colonized beneficial bacteria on its surfaces, and can make for great seeding material. I wouldn’t put one in a filter (in fear of hurting the moss ball) but they can help with the nitrogen cycle.

5. Requires Almost Zero Maintenance

The moss ball requires freshwater, some amount of lighting (prefers shading in bright tanks) and waste to feed off of. So basically, as long as you have an aquarium set up with aquatic animals, you’ve already got everything the algae ball needs. Every time you feed your fish, you are also feeding the moss ball, so no fertilizers are required.

There is only one task that must be done for a Marimo: it needs to be squeezed outside of the tank every once in a while. Yes, you should actually squeeze it (as you can’t do with the cheap Java knockoffs).

The Marimo sucks up a lot of filth and debris over time (like a sponge), which is a good thing. But it also absorbs more than it can chew, and the nasty stuff eventually leeches out. So every time you perform a partial water change, just remember to take out the moss ball, squeeze it over a bucket or sink, and toss it right back into the tank. It will float at the surface for a while unless you squeeze it again while underwater. Floating does not hurt the Marimo. In fact, the balls can float up to the surface on their own from internal gasses, as well as sink on their own.

There is technically another task for the moss ball: it should be moved around once in a while to keep its rounded shape, as well as to provide some lighting on every surface to avoid dead patches. But if you are performing routine gravel cleanings and squeezing the moss ball every week or two, then you’re accomplishing this anyway.

So yeah, squeezing the ball once in a great while is the only maintenance required.

Video: What Is a Marimo Moss Ball?

6. Easily Adapts to High pH

A lot of aquarium plants don’t do so well in high pH water, but this doesn’t affect moss balls. I have kept moss balls in pH of 8.4, and they remained healthy.

7. Is Beloved By Shrimp (and Other Creatures)

Because the moss ball collects debris and nutrients over time, small freshwater shrimp enjoy scavenging through the green stuff and munching on any particles to their liking. I have also seen African Dwarf frogs lying on top or snuggling underneath the moss ball. Floating moss balls can even serve as toys for betta fish since they like moving the ball around. All in all, critters can use this ball of algae as a smorgasbord, a comfy hiding place, or a means of entertainment.

8. Is Snail-Proof

Some snails like to munch on live plants, resulting in dead organic matter that needs tossing out. Fortunately, they don’t harm the moss ball. I have had mystery snails, Malaysian Trumpets, Ramshorns, Zebras, and pond snails, and none of them damaged the Marimo. Snails sometimes nibble on the moss ball, eating food off of it like shrimp.

9. Does Not Produce Dead Matter

Lots of plants grow new leaves and lose old ones simultaneously—that's the sign of a healthy plant. But this also means having to remove the decaying parts of the plant from time to time, unless you want your nitrates to go up. No such maintenance for the Marimo! As long as they are healthy, moss balls stay green and intact.

10. Tolerates Salt Well

Aquatic plants don't do so well with salt. Freshwater aquarium salt can be used to treat various injuries and parasitic outbreaks, as well as keep nitrites down during mini cycles. Salt can actually benefit moss balls, as they are known to live in brackish water.

11. Does Not Bring Hitchhikers With It Into the Tank

When buying live plants from the fish store, you're often buying other creatures with it, from pond snails to tiny creatures not visible to the eye (such as parasites). Luckily moss balls are, for the most part, sold in individual cups. This minimizes the chance of unwanted residences in your fish tank.

12. Doesn't Need to Be Anchored

This is probably one of my favorite benefits of the moss ball, aside from the incredibly low maintenance. A lot of plants need to be anchored, by either burying their roots in gravel or tying them to an object until it attaches itself (which takes patience). It can be a chore removing anchored plants in order to clean the gravel. I would remove my Java Fern and afterward try to bury it again, which often took a few tries because I have a thin layer of gravel. While struggling to bury all the roots, some small amounts of debris would kick up and that would be really frustrating. It got to the point that I’d just avoid repositioning by vacuuming around it.

The moss ball isn’t meant to be anchored. It doesn’t need to be removed when cleaning gravel. It can merely be pushed aside by the siphon with no damage, and it’s one of the few items I don’t have to remove in order to do a thorough clean.

13. Almost Impossible to Kill

The only way to kill a Marimo is if you place it in water full of chlorine (such as untreated tap water), saltwater, or a cesspool (where there are no nutrients in the waste).

In other words, as long as you keep up with your maintenance on the tank, providing nutritious food for your animals, the moss ball will thrive. Remember that they prefer dim lighting. White specks on them indicate over-exposure to light. If they have brown patches and/or float up on their own, this means they are not getting enough light (a problem I've never had with them).

Are There Any Disadvantages?

1. It Doesn't Affect Large Tank Health

While it has the same benefits as plants like absorbing nitrates and providing oxygen, the moss ball does these things on a smaller scale, at least compared to the bigger plants out there. To make a large dent on nitrates, oxygen levels, and the prevention of algae, tanks often have more than just a few plants when we get into double-digit gallons. Often a tank is filled with different species of plants to make a significant impact on tank levels.

To do this with the Marimo, you’d have to fill 1/4 of the tank with moss balls, and that would just look odd. That or have a moss ball the size of a bowling ball.

So if you only want algae or nitrate control (while the moss ball can contribute), you’d have to buy plants in addition. The Marimo just helps with these problems; it doesn’t solve them on its own. So don’t think a single moss ball in a 20 gallon is going to make a significant impact on your tank.

2. Goldfish Eat It

Goldfish are known to eat anything in their paths, so don’t be surprised if your goldfish tears this ball to shreds.

3. It Is Slow-Growing

The Marimo moss ball is the slowest growing plant I’ve ever seen. I’ve heard they can get to be the size of softballs or even bigger, but it takes years (closer to decades) with an enriched environment to get to that size. So if you want a larger ball, you’re in for a wait. If a moss ball is too big, they can be torn apart, resulting in smaller moss balls. You’ll have to regularly move them to make those irregular bits round again.

Of course, this means if you love the size of your moss ball, it will stay that size for a long time.

4. It Does Not Reproduce

While aquatic plants spawn over time, Moss balls won’t reproduce in your tank—they just get bigger. So you won’t find little baby moss balls or patches of the algae. This can be good or bad depending on what you want. Only tearing one apart will result in more moss balls, but I'd suggest just buying more. It can be years until a baby moss ball grows to golf ball size.

The Verdict

Overall this is a great little plant substitute for those of us who have difficulty with aquatic plants. I suggest having more than one in a tank if you want those benefits that plants have. If you want moss balls purely for decoration or as an addition to plant life, they are safe, fool-proof organisms that can only benefit your tank.

More by this Author

Comments 36 comments

Hugh Guestit 3 months ago

I once had Marimo ball in a 55 gal tank that I ripped apart...It grew astronomically fast. I accidentally used the net I use with my 55, on my 40, and a piece of Marimo must have transferred...but it has grown at a MUCH faster rate than what anyone else says online...I actually am looking for a way to destroy it because it is overtaking the 40 gal, and I have plants in that tank. The tank gets dry ferts too, so that doesn't help at all...The only viable option has been to manually remove bits of it, and it is indeed, positively, Marimo "moss"

Alyssa 6 months ago

I bought my Marimo for $8

Ned Pepper 6 months ago

This article is more fiction than fact. Marimo are stealth predators eating any fish that gets too close ... they stick to the spiny tendrils and get sucked in. If you notice a fish disappear, and a skeleton lying by your Marimo, just know that it was not a friendly collision.

Kellie Simms 7 months ago

You're Moss Ball information is and has been exactly what I was looking for, thanks so much for the information and may be of our Green Moss Balls grow!

Doreen 7 months ago

Great article! If it's suppose to control algae, would it be smart to not put one in with algae eaters?

Linda Robinson 7 months ago

Hello Marie, excellent hub. It is fascinating and extremely informative, everyone and anyone interested in tanks, and fish should definitely read your hub, so much terrific information. So nice meeting you. Linda

BirdieGal 8 months ago

I have a 2 gallon tank with a filter for my betta fish. I had two small plants in it that I struggled to keep going and some amount of algae on the rocks on the bottom. I was finally able to find real Marimo moss balls at my local Petsmart so I grabbed one when I went looking for a new plant for Phinnigan. Bought one plant and the ball. Did a complete cleaning of tank, rocks, etc.. The tank has never looked better. It has been in there for 2 weeks now and nothing...NOTHING is starting to grow on the bottom and the water is crystal clear. I wondered what the exact benefits of the ball were so I searched and found your article. Great job, very informative. Phin loves his ball and will even rest on it. I don't suppose another one would hurt so I will pick up one more. Love the way they look as well!

jupiter justice profile image

jupiter justice 8 months ago from Los Angeles, CA

This moss ball is such a great addition to an aquarium. It adds to the aesthetics to the natural habitat but very beneficial as well. Great write up and very informative. I love this hobby and have had both fresh and saltwater aquariums with live plants and fish. It's very therapeutic to the soul and mind. Cheers!

howlermunkey profile image

howlermunkey 8 months ago from Tampa, FL

Awesomeness! can I put one of these in my Koi pond? The PH is high, water is filtered etc., but is of course outdoors (though within a semi-closed patio-deck). I have a small pond for the baby Koi, wondering If I could put one of these in that for starters?

Jlbowden profile image

Jlbowden 8 months ago from Long Island, New York

Very interesting and useful article about the Marimo moss ball. I had something similar in my freshwater aquarium. However it was sold at Petco where I picked it up about a week ago.

It was suspended on a nylon string attached to a rock to weigh it down. So this right away tells me it was basically some sort of floating plant used mainly as a tank ornament.

However when I stopped into another Petco today, I did come across the Marimo moss ball. They were selling it under the name fluval moss ball though. And so I bought this golf ball sized moss ball - possibly an imitation for $5.99 And not the $18-23 you mentioned near the beginning of your article.

Wish I could attach a pic to my comment here. But do not see a feasible way to do so. So anyway I placed the fluval moss ball in my tank this evening. Had to squeeze it a bit to get it to finally sink to the gravel bed on the bottom.

So I will see if this is similar to the Marimo Moss ball, or a imitation in which fluval used their name on. Otherwise still interesting stuff and congrats on your article making Hub of The Day. Now that's something really worth talking about!


ignugent17 profile image

ignugent17 8 months ago from Central Illinois , USA

Congratulations hub of the day!

RTalloni profile image

RTalloni 8 months ago from the short journey

Such an interesting tank plant to learn about. Congrats on your Hub of the Day award!

Kristen Howe profile image

Kristen Howe 8 months ago from Northeast Ohio

Marie, congrats on HOTD! This was real interesting to know about these aquatic plant. I never heard of it. But it's so useful and resourceful to keep it clean. Thanks for sharing.

ChitrangadaSharan profile image

ChitrangadaSharan 8 months ago from New Delhi, India

Congratulations for HOTD!

This looks like a great little plant substitute for those of us who have difficulty with aquatic plants.

I do have a fish tank but do not keep aquatic plants in them since they usually do not survive. Good to read your hub and learn about the benefits of the Marimo Moss Ball.

Thank you for sharing this useful and informative hub!

josefinamoe 8 months ago

Very interesting and helpful article. Recently, I have order an aquarium from which contains marimo. Your article help me to better understand the advantages of it.

mariekbloch profile image

mariekbloch 13 months ago Author


Pollyanna Jones profile image

Pollyanna Jones 13 months ago from United Kingdom

Very useful! We're still getting our new aquarium to settle before adding fish, but we have purchased one of these balls a month ago. For now, it'll have to be our pet, as the Japanese view them! So glad to read of its benefits. Thank you for sharing your knowledge.

mariekbloch profile image

mariekbloch 13 months ago Author

Hi AccaliaJay, filters only come into effect after a month of use (which by then grows enough beneficial bacteria to detoxify ammonia). The moss balls will help in between water changes until your new filter has been in use for a month. Is it possible the filter's currents are too strong and he gets tired out? I'd look into internal air filters, like sponge or box filters, which you'll probaby have to buy online. Until that month of use, I'd do a partial water change every day and add a few drops of Prime in the tanks, a dechlorinator and detoxifier found in Petsmart, Petco, and local fish places. Small bottles are usually $5. Also check out my other hubs like "Top 10 Mistakes New Fish Hobbyists Make" and "How to use Box/Corner Filters" for more information on filters and maintenance. Thanks for the comment.

AccaliaJay 13 months ago

Hiya! Thanks the amazing info. I just ordered 5 of those little things from ebay I have two 5 gallon tanks. One has a single betta named Blaze and the other has a betta names Liberty and a guppy named Hadifer. I had 3 other guppys but they've passed on through the span of 5 months. Blaze keeps becoming ill when I put the filter in his tank so I've decided to not use it again cause someone said some cartridges release bad stuff back into tanks later on. And I don't have the money to buy replacements so I'm hoping these things will help clear up any no good water problems while we get money to buy the replacements. And I've been having algae problems in both tanks so I'm hoping these will help. Just need to decide whose getting the extra. Might float one in each tank for the bettas while the others sit on the bottom.

mariekbloch profile image

mariekbloch 14 months ago Author

If you found it in saltwater, then it isnt a marimo, unless someone threw it in there. Most likely another type of algae or plant. Keep it in saltwater for now and observe it. Make sure there are nutrients in the water, like adding some fish food.

kym 14 months ago

We found a believed marimo on the Golf Coast of Florida. I had no idea what it was but was intrigued right away. It definitely has some friends attached and I was fearful it would die with out help. So right now I've left it in the salt water until I can research more. Any suggestions on removing parasites etc.? Should I change it to freshwater.

doris 15 months ago

my marimo did have a baby and grew quite a bit probably because i use salts in my tank. they went from one inch to 5 inches across. over 3 years.

lyoness913 profile image

lyoness913 16 months ago from Overland Park, KS

This is very interesting. I would never ever think to look into something like this, but I will now buy one for my fish tank.

Thanks! Voted up and useful.


Chance Harvey profile image

Chance Harvey 16 months ago

These look really cool, I want one for my fish tank.

MonkeyShine75 profile image

MonkeyShine75 17 months ago from Los Angeles, California

Very interesting hub, thank you for the information

Voted up

mariekbloch profile image

mariekbloch 17 months ago Author

I wander if it's a lack of filtration? Filters with sponge or filter floss inside them will clear the water up fast. A moss ball may help.

mariekbloch profile image

mariekbloch 17 months ago Author

I understand your frustration. Try Amazon or Ebay, although it's rare a seller will only sell one. Look out for pieces of white (the plastic part in a java moss ball). Also Marimos look like green balls of fur underwater, not stringy-looking like it can fall apart.

hrymel profile image

hrymel 17 months ago from Fort George G Meade, MD

I have a Beta whose tank keeps getting cloudy really fast. Maybe I'll try one of these to even things out in his little home.

Misty 17 months ago

Where can you buy them online where you know they're real? I don't know if i can trust my pet stores. Is there a way to tell if it's a fake just from looking?

mariekbloch profile image

mariekbloch 19 months ago Author

I've never owned a saltwater tank, so I don't know for sure. But I believe they are freshwater only.

Abigail 19 months ago

i just have one question, im thinking of getting a saltwater aquarium and what not so i was wondering can the marimo survive?

jaquivion 19 months ago

Cool plant i have one got it from petsmart my favorite and pecto

Sunny 19 months ago

Will Marimo reproduce? Is that possible to split it in two?

Yes, Marimo will reproduce when it is kept in a large pool of water. However, it is not recommend splitting up your Marimo. Very often you may damage it and it can cause it to die :( If you are lucky your Marimo would reproduce and you would see a bump growing on your Marimo. Congratulations for that is your baby Marimo!

mariekbloch profile image

mariekbloch 2 years ago Author

Zebra snails are a type of nerite. It won't hurt it at all.

Fishytheguy 2 years ago

Hi. Im considering getting 2 mossballs from my petstore. The tank size and fish speicies are compatible, but i have a nertite snail and i don't want him to eat it. He doesn't touch my anubias, water wisteria or amozan swords, but i just wanna check with u to make sure its alright.

Neomar Dethron profile image

Neomar Dethron 2 years ago from Puerto Rico

Very good Hub.

    Sign in or sign up and post using a HubPages Network account.

    0 of 8192 characters used
    Post Comment

    No HTML is allowed in comments, but URLs will be hyperlinked. Comments are not for promoting your articles or other sites.

    mariekbloch profile image

    mariekbloch43 Followers
    40 Articles

    Marie is a lover of everything about and inside of aquariums. Among other friendly creatures, she has a turtle that she adores.

    Click to Rate This Article